text:
What is the difference between a nautical mile and a statute mile? And what is a knot?
What is the difference between a "nautical mile" and a "statute mile?"
And what is a "knot?"

I disagree, the answer to what is the measurement system used in aviation is different than the definition of the unit of measurement itself. I searched the questions and didn't find this question so I decided to contribute it. I'm asked this question all the time by laypeople so I figured it may be useful to have it on this site.

Nautical mile, statute mile, knot. You're expected to do some basic research before posting.

I did basic research, and discovered that this question was not answered on this site. Just because wikipedia has a page on the topic, doesn't mean that we are not allowed to post it here.

Just because an answer to a question can be found on wikipedia doesn't mean that it shouldn't be asked or answered on this site. Any question that is useful and results in increased traffic and visits improves our site.

According to the Encyclopedia Britannica a nautical mile used to be based on the curvature of the earth and was approximately equal to one minute (arc segment) of latitude along a meridian (longitudinal line running from north to south). The British nautical mile was set to 6,080 feet while the US nautical mile was set to 6080.20 feet. However, in 1929 the nautical mile was redefined to exactly 1.852 km (approximately 6076.11549 feet) at an international conference held in Monaco, although the US didn't make the conversion until 1954.
1 nautical mile = 1.1508 statute miles or 1.852 km.
A "knot" (speed measurement, not the kind you tie in your shoe laces) is equal to one nautical mile per hour.
1 knot = 1.15 miles per hour.

@Pete that is cool. I wonder if there is a youtube video of someone demonstrating that old world method of measuring knots.

There's a lot of pirate movies (Pirates of the Caribbean) en tv series (Black Sails) where you can see this method used on ships. In aviation it seems to be less practical.

There are basically two different categories: nautical units and statute units.   A few times early on in my aviation career I mixed the two (especially easy if you fly in a plane that uses mph but you measure nautical miles on your sectional) and it will yield inaccurate numbers, which can be pretty dangerous, depending on the calculation you are doing.   These are the three main kinematic units that relate to motion of each category and values you can use for conversions:
Category: nautical/statute;  (conversion values)
Speed: knots/mph;   1/1.15
Time: hours/hours;   1/1
Distance: nautical miles/statute miles; 1/1.15
These all follow the equation distance = speed * time (as long as you do not mix and match the category (nautical units with statute units or vice versa).
Historically speaking, the nautical units were used by sailors because it was just more practical -- one nautical mile was originally defined as one minute of latitude (lines of latitude are the ones that slice the earth horizontally -- think "flatitude"), a distance which is relatively constant (although not totally so due to earth's ellipsoid shape, but much more so than minutes of longitude which vary greatly).   This was more convenient for sailors to use than statute miles because latitude (as well as longitude) was frequently used to define position so it was easier to use for dead reckoning and navigation.   Lines of latitude one degree apart are about 69 statute miles apart on the surface of the earth (varying slightly depending on your location on the surface of the earth), so one minute of latitude (1/60th of a degree of latitude), is about 1.15 statute miles apart on the surface of the earth (69 statute miles/60, because a minute is 1/60th of a degree).   Since a nautical mile is defined as the distance of 1 minute of latitude, it turns out that 1 nautical mile is equal to 1.15 statute miles.   The actual value now is set at about 1.15078 statute miles because the nautical mile was redefined to be exactly 1852 meters (now internationally accepted).   Etymologically, the term derives from sailors counting the number of knots in the rope that unspooled from the reel of a chip log (basically a spool of rope) in a specific time.   Aviation follows many naval conventions, nautical units included.

When you think of miles in normal life (20 mile drive, a mile run, etc.) those are all statute miles.   Usually in aviation as well as in naval applications the units belong to the nautical category (20 nautical mile flight, 120 ktas (knots true airspeed)).   Recently, however, some plane manufacturers have made a move towards using statute units in their manuals/avionics so keep an eye out for units, especially on more modern planes.   As far as the aviation systems (what category weather reports use and what controllers use), everything is in the nautical category except for measuring visibility (you would hear wind readings at 10 knots from 160 degrees for example but a visibility report at more than 10 statute miles for example).
A similar important distinction (not related to statute vs nautical) is that when you READ angles (degrees on a winds aloft forecast or a METAR) the degrees are usually with reference to TRUE north (for flight planning purposes).   When you HEAR angles (ATIS report, controller wind report) the degrees are usually with reference to MAGNETIC north.   Anyway back to nautical/statute.
If your plane does use statute units there is most likely a statute mile side of your plotter (so you can measure statute miles on your sectional as well as nautical miles) -- use this instead of trying to convert the units; it will save you time and mistakes.   Also most airspeed indicators can read both knots and mph, although the outside ring is the one belonging to the category that is most likely dominant in the manual (in values for cruise speeds, etc) -- in this case mph.

I hope this helped -- fly safe.

I'm confused by this statement One degree of latitude is about 69 statute miles (varying slightly depending on your location on the surface of the earth), so one degree of latitude (a nautical mile) is about 1.15 statute miles (69 miles/60 minutes; there are 60 minutes in a degree).  You seem to be defining a degree of latitude twice as two different values.  Is this a typo or am I just not comprehending?

To clarify -- minutes are just a smaller measurement of angle than degrees -- for instance there are 60 minutes in 1 degree just as there are 100 centimeters in a meter.   Miles are not a measurement of angle, they are a measurement of distance.   When I say 1 degree is about 1.15 statute miles I mean two adjacent lines of latitude (1 degree apart) are separated by a distance of about 69 miles on the surface of the earth (a mathematical way to describe this is "arclength" rather than angle)...

... Because of this we can reason that (since one minute = 1/60th of a degree) one nautical mile, defined as the distance on the earth's surface between minutes of latitude (or the arclength of a minute of latitude) is 1/60th of 69 miles, or about 1.15.   So one nautical mile is about 1.15 statute miles.   Just trying to show why it was useful to sailors (and to pilots) -- they could convert nautical units easily to minutes of latitude.   I will update my post to make this clearer.

(Ignore this if you don't care about math) -- It actually turns out that since the earth is a sphere, the arclength of a minute is actually not perfectly 1/60th of the arclength of a degree but since the earth is so huge its close enough that we can say it is.   That belongs more on math stack exchange though.

So shouldn't the sentence read "One degree of latitude is about 69 statute miles (varying slightly depending on your location on the surface of the earth), so one minute of latitude (a nautical mile) is about 1.15 statute miles (69 miles/60 minutes; there are 60 minutes in a degree)"

Ah yes now I see my mistake -- I meant to say one minute -- thank you for catching that... I guess I just overexplained it for nothing.

No worries, very informative answer!


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How soon can I start my turn after reaching the missed approach point, when missed approach procedure calls for a climbing turn?
If the missed approach procedure only calls for a climbing right hand turn, at what altitude after reaching the missed approach point (MAP) can I initiate the turn on a precision approach that takes me down to 200 AGL.
Some missed approach procedures say, for example, climb straight ahead to 1000 then climbing right turn to 3000, but some just say climbing right turn to 3000.
Is it documented anywhere that in this situation you can immediately start your climbing turn from the DH (or MDA on non-precision approach)?

Can you give an example of when the MAP says to turn immediately when you are on a precision approach? I can’t think of any offhand but I don’t fly where it’s flat, so that may be why.

@JScarry I'll see if I can find it, but I came across it when doing some approaches on simulator a while back at various locations in US. I thought to myself, thats kind of scary (no pun intended). But maybe I mis-remembered it. All the approaches I remember form my time in CA had a climb out straight ahead before turning.

@JScarry: Here's a (now-closed) partial example; the missed-approach procedure calls for a hard right turn immediately upon reaching the MAP (the IGS middle marker) to avoid flying into a mountain, but the non-missed approach also calls for a sharp turn there (for the same reason), hence why it's only a partial example.

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text:
Myth or Fact? U.K pilots struggling for work while U.S big airlines are kicking down the door for pilots with an American passport
Myth or Fact? Why are U.K/British pilots struggling to find their first job, then once they get the hours are still struggling? The question Is... Is it easier to get a job being a American Aviator Or British Aviator. For Aviation
There are even TV Shows about pilots having to travel across the world just to find work with a British passport. Worst Place To Be A Pilot - Season 1 / Episode 3 - Full Episode
Meanwhile, CNN posted an article that U.S American pilots are in heavy demand and big companies are practically kicking down the door for new pilots. I list my sources so you know what I'm talking about.
Is it a fact that U.S student pilots are having trouble paying for training with the U.S economy or is it because there are harsher rules for Americans so now less people are meeting the requirements? Are older pilots retiring? etc.

 I would hyper link but I don't have enough reputation points

Here are the sources-------[link] (http://www.ft.com/cms/s/0/d7117f1e-d963-11e5-a72f-1e7744c66818.html#axzz46uLwU7s4)  (http://learningenglish.voanews.com/content/us-pilot-shortage/3229183.html) (http://money.cnn.com/2016/03/07/pf/jetblue-pilot-training-program/)

US requires 1500 hours for the first officer. And that is a crazy amount of hours.

I'm voting to close this question as off-topic because the it's about commenting broad news and corporate communication rather than an actual question. Rework it so that this is an actual question.

Sounds like this would be a better fit on Skeptics.SE, any way

Cathay Pacific and Dragonair have offered free pilot training for those who has no experience for a long period.

authors: Глеб Сергеевич Гущо

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Why it was thought that 25% of the passengers could have survived the Crash in the Desert?
I read on Wikipedia:

The Controlled Impact Demonstration (or colloquially the Crash In the Desert) was a joint project between NASA and the Federal Aviation Administration (FAA) that intentionally crashed a remotely controlled Boeing 720 aircraft to acquire data and test new technologies to aid passenger and crew survival. The crash required more than four years of preparation by NASA Ames Research Center, Langley Research Center, Dryden Flight Research Center, the FAA, and General Electric. After numerous test runs, the plane was crashed on December 1, 1984. The test went generally according to plan, and produced a spectacular fireball that required more than an hour to extinguish.

This test was conducted to see (amongst other things) if some stuff could temper the flames after the crash. Obviously it couldn't.
It is written:

FAA investigators estimated that 23–25% of the aircraft's full complement of 113 people could have survived the crash. Time from slide-out to complete smoke obscuration for the forward cabin was five seconds; for the aft cabin, it was 20 seconds. Total time to evacuate was 15 and 33 seconds respectively, accounting for the time necessary to reach and open the doors and operate the slide. Investigators labeled their estimate of the ability to escape through dense smoke as "highly speculative".

If I look at the video it seems quite impossible to survive such a crash. But not for the reason critics gave above (the smoke would be too heavy). Of course it is not a crash that results from falling down straight out of the sky. It is more a crash landing. But it looks as if you just can't survive such a crash. But looks can deceive...
How did they arrive at 25%? Are there real-life crash landings that are comparable? There was a huge load of fuel in the plane. Was the test meant to see what happens if a plane has to return right after the start?

In short
The controlled impact demonstration (CID) had two main objectives:

To evaluate antimisting kerosene (AMK) effectiveness on containing fuel fire propagation after a landing resulting in damages to fuel tanks and fuel ignition. This was the only initial objective.

To evaluate floor and seats behavior during crash (crash-worthiness). This objective was added as the initial objective offered a good opportunity for it.

The landing conditions were designed to damage tanks and ignite fuel. The impact was moderate only as "rhino" horns where installed immediately after at the impact point to make an incision in the fuel tanks and engine:

CID rhino barriers, source F.L. Fulton / NASA
23–25% doesn't tell about how many persons could have survived the crash mechanical effects, but how many could have evacuated before losing consciousness due to smoke, disregarding any impact injury/fatality.
Does that happen in actual accidents? Yes, in the British Airtours Flight 28M, 55 people died in an aircraft stopped on a taxiway with a punctured fuel tank.

Smoke and time for evacuating
When in the middle of a fire, the two deadliest hazards are not flames themselves but smoke and hot air. Smoke by itself brings deadly CO and reduces O2, but also triggers a coughing fit preventing, within a couple of minutes, further O2 extraction, leading to incapacitation.
The conclusion you mention only evaluates the number of persons able to evacuate the aircraft before losing consciousness. Related assumptions are detailed in the report, page 55:

Unfortunately there has been many fatalities during actual evacuation of cabins in fire, due to smoke. In particular there was an accident a few months only after the CID, this accident did happen during the takeoff attempt, the aircraft did not even leave the runway and no damage occurred except a puncture to a tank. Still 55 persons died because of the smoke:

What do we know about the survivability aspects  of aircraft accident evacuations and how did the industry learn lessons in this area?
One significant accident that contained lessons for the aviation industry and led to changes occurred in 1985 at Manchester Airport in the United Kingdom.
During take-off, at a speed of approximately 125 knots, the left engine of a B737 suffered an uncontained failure which caused a fuel leak. The leaking fuel ignited and burned directly behind the left engine. The take-off was abandoned and the aircraft exited the runway on the right hand side onto a taxiway, which resulted in the wind directing the fire towards the aft fuselage.
The airport fire service attended the accident site promptly, but within 5 and a half minutes after the aircraft came to a stop, of the 137 passenger and crew onboard, 55 persons had lost their lives.
“The major cause of the fatalities was rapid incapacitation due to the inhalation of the dense toxic/irritant smoke atmosphere within the cabin, aggravated by evacuation delays caused by a forward right door malfunction and restricted access to the exits.

Source.
More information on this accident on Wikipedia.
Incidentally this accident also tells us something important about cabin crew members role, training, and effectiveness to help people evacuate the cabin at their own risks. In the Manchester accident, cabin crews, which two members died in the accident, were awarded a Queen's Gallantry Medal along with firefighters. At the time they were officially known as "steward/ess".
Floor and seats behavior
A specific experiment was conducted on the seats, to compare standard seats of that time (-9g forward), and improved ones (-18g forward).
Both FAA and NASA concluded CID was a survivable accident (Summary report, page VII) and in the detailed report (on page 31) that the impact conditions were overall mild (thus preventing to fully compare seat performances).

The test objectives which involved the recording of data pertaining to the airframe structural floor loads and seat occupant responses during impact were met. However, because of the mild impact conditions, the objective to demonstrate the performance between the standard and modified seat designs was not completely satisfied.

Dummy bodies set at various locations in the flight deck and the cabin were severely shaken (as visible in this recording, starting at 1:48), but these accelerations were deemed survivable.

It was assumed that everybody survived? Well, it is a landing indeed. And I guess you would be alive indeed shortly after the landing. But by the looks only it seems nobody could survive. Maybe next time they should do it with a life-crew and passenger load... To test the prediction...Anyhow, +1

@DescheleSchilder: I added some data from actual evacuation, I remember having heard of several deadly evacuations.

So smoke is even more deadly than fire? It goes everywhere. The flames are pretty located. Would many people have survived without smoke? If so, cant you better use hydrogen as fuel? Its clean alsi. I mean also ( the dials on my phone are so /#@=%! smal...

Hydrogen may burn "purely", but it burns explosively. No survivor in such a case.

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Are instrument lights required for night VFR flight in an SLSA?
Our flying club is operating an SLSA that has all the exterior lights as required by FAR 91.205(c).  But don't the instruments that are also required by 91.205(b) need lights as well?

note SLSA planes are not operated with a "standard category U.S. airworthiness certificate", as 91.205(a) targets. It comes back to op limits from the manufacturer- for instance, the RV12SLSA POH says "Night flight is prohibited (unless equipped with optional lighting)."

An SLSA does not have a "standard airworthiness certificate," and thus 91.205 does not appear to apply at first glance.
However, 91.327(f) applies:

The FAA may prescribe additional limitations that it considers necessary.

Some of these "additional limitations" can be found in FAA Order 8130.2J:

Night flight and instrument flight rules (IFR) operations are authorized if allowed by the AOI and if the instruments specified in § 91.205 are installed,
operational, and maintained per the applicable requirements of part 91.

This is a standard "operating limitation" for SLSA aircraft, and so should appear on the special airworthiness certificate, and means that 91.205 applies to SLSA the same as for normal category aircraft, when used for night or IFR flight.
That said, cockpit lighting simply isn't legally required by part 91 for night VFR flight. Unless it says otherwise in the POH, flying without cockpit lighting is perfectly legal. But remember that legal doesn't always mean safe!

Cockpit lighting is not required to be present as required Night VFR equipment under Part 91 general flight rules.  That being said, there is the following Part 23 Certification Requirement for external and cockpit lighting.

§23.2530 External and cockpit lighting.
(a) The applicant must design and install all lights to minimize any adverse effects on the performance of flightcrew duties.

Under the terms of this regulation one could make the argument that an OEM applying for a normal category type certificate will need some type of effective cockpit illumination to minimize adverse effects on aircrews.


text:
Can the FAA 8130-3 have "modified" status if a part is converted by replacing piece-parts from IPC?
I have been trying to identify if the FAA 8130-3 Instructions have some clarity but am unable to deduce if this situation is indeed acceptable. A sequence of events (Of sorts) is given below:

A Part had a defect and was removed as Unserviceable and shipped to Shop
The Shop has replaced certain piece-parts which are fitted on a newer design
The Shop has then released the original part with the FAA 8130-3 stating "Modified" in Block 11
As per the Shop, the replacement Modifies the part and the status in Block 11 is acceptable


text:
What is the best procedure for landing at my destination if I have a full electrical failure at night?
What is the best procedure for landing VFR at the intended destination airport and I have an electrical failure, in the following scenario?
Let's assume this is a VFR flight and I'm 50 miles from the departure airport in the United States, which is a cross country flight. There is no issue with the weather. I have noted no issues with the Cessna 172's electrical power at run-up prior to takeoff, I have at least an hour of fuel reserve and meet all the 91.205 requirements.
I then experience an electrical failure during the en-route phase to the intended destination airport, and I have done the necessary checklist to try to solve the issue but it doesn't fix the problem. As I approach the vicinity of the airport, I key the mic seven times (high intensity) and no runway lights appear. I expect it is too risky to land on the road because there could be power lines nearby.
I found the following scenarios on the internet but they don't answer my question:

Pilots flying to a towered airport (still open at night) with full electrical failure, squawking 7600, and waiting for ATC's light gun signals to appear.
A pilot has the same issue and is lucky when a plane turns on the runway lights and lands before him, but he doesn't commit an emergency
The pilot is lucky at landing at a towered airport that is closed while the lights are still on, but the lights turn off or dimmer to pitch-dark as he begins to land

I came up with my scenario myself because I can't find information about it on the web. It would help me if you could provide suggestions and tips on what I should do or not do when this happens to me in the future.

In this scenario, can you still see the runway? Because I would much prefer landing on an unlit runway compared to a highway.

Consider editing this question to make it more clear. There are something like 6 different scenarios presented here. Consider listing them out in separate bullets to make it easier to parse the information you need.

There is no right answer because there are simply too many variables. (Ambient moonlight, size of runway, pilot's familiarity and experience, etc.) It's a judgement call, but a good discussion to have, and will give you more ideas to be prepared and make the best decision if that time ever comes. One option not mentioned is returning to departure airport if that is best... 50 miles isn't that far.

That’s why I carry a pair of NVGs with me all the time just in case.

Do you have a cell phone? I once had a pilot experiencing a full electrical failure who had the number for the local briefing office in his phone, and they simply forwarded the call to the tower so I could talk to him directly

Welcome to aviation.SE! Can we assume from your mention of 91.205 that you're asking about the US? And is this flight IFR or VFR? You've tagged it as both, and IFR has formal lost comms procedures that VFR doesn't.

Keep flying until daylight, so you can see better ?    (humour)

It actually happened to this pilot.

How do you squawk 7600 if you don't have electricity?

Here's an investigation report on this very sort of thing in Canada.  Note that the standard procedure to alert ATC that you have a total electrical/comms failure is to fly a left hand triangle twice with 2 minute legs, every 20 min.  If they can see your non-transponder target they will quickly get the idea, and then make allowances for whatever you do next  As with IFR comm failure procedures, you should be careful to make the "next" thing you do the most logical thing for the controller to expect.
If there was an operational controlled airport with lights that was the only safe place to go to get down in one piece, I would proceed there doing the triangles, then when in visual range of the tower do another triangle until I got the flashing green light from the tower. And if I didn't get the light, and I was running out of fuel, I'd just go ahead and land.
Important thing to remember in aviation is that the regulations aren't a suicide pact, and once it's life or death, you do what ya gotta do, end of story, and while you may have to do a lot of report writing, if you crossed some lines taking reasonable action to save yourself and passengers, you won't get busted for that - hopefully.
If you're stuck with no other airport to go to with lights, and your darkened destination is the only option, well, you kick yourself for being so foolish as to fail to make allowances for that eventuality (which is not really that improbable), take your chances, and hope it turns out.
Of course, it is the early 21st century, so you should have your phone with you no?  So unless you left it behind or the battery is dead, call somebody. The destination airport operator to turn the lights on.  Someone you know there that can light up the runway with a few cars.  An air traffic control unit.  911 even.

Not a pilot - so you fly a triangle which takes six minutes, every 20 minutes? What do you do for the intervening 14 minutes?

Go where you're going.  It's something you do while onroute.

@AzorAhai--hehim I think it's "fly two triangles (each taking 6 minutes), then continue flying as normal towards destination for 20 minutes, then repeat", based on reading the link

While full electrical system failure is uncommon, it does happen. It has happened to me personally on a flight over north Texas, due to an alternator failure. It's important to discern the cause as best you can and assess the remaining resources at your disposal. For example, in my case, I was able to preserve the remaining battery power by turning off all electronics until I reached my destination, only reactivating my transponder and radio when it was time to enter the mode C veil, notify ATC of my predicament, and request landing clearance.
Remember, if you truly have total electrical system failure, including no battery power, your radio and transponder will not be operational - so keying the mic to activate runway lights will not be an option, and neither will squawking 7600. This is why it's always a good idea to bring a backup handheld radio with you in the cockpit.
Unless it involves a fire, electrical failure does not affect the aircraft's ability to fly, so landing off-airport should not be necessary. If your transponder and radio are dead, landing at an uncontrolled airport is probably your safest bet. Most of the time, traffic is extremely light at these airfields during the evening hours, and some leave the runway lights on from sundown to sunrise. You did bring your AF/D, Sectional Charts, and a flashlight on this night flight, right? Just navigate to the best, closest option with adequate lighting, and observe from a distance - other aircraft will probably not see you with your lights out, and you won't be able to listen for traffic advisories on the comm. Once you're certain that the pattern airspace and runway environment are clear, you can make your landing. Keep in mind that you will not have a landing light, and the dark runway can come up at you quickly. Keep your descent shallow and slow, and be prepared to tease the runway as much as possible using the edge lights as a reference to avoid a hard landing.
Now that you're safely on the ground, wait 2 weeks, then tell your story over beers and make it sound like an epic adventure.
ADDENDUM:
Some pilots disagree with the use of an uncontrolled field under these conditions. Ultimately, as the PIC, it is always up to you to determine the safest course of action and always fly within the limits of your own experience and preparation. If you do decide to proceed to a controlled field, this is, of course, a perfectly acceptable option. With no radio or transponder, you should remain outside of the Class D until you can determine the direction and flow of traffic. Then and only then should you enter the traffic pattern while maintaining visual contact with the tower, watching for light signals. Because this is a nighttime scenario with dead electronics, the tower will likely not be able to see your acknowledgment of these signals via wingtip dipping, nor will you be able to utilize your aircraft lighting. It is likely that ATC will quickly ascertain your compromised state and will coordinate traffic separation and pattern clearance on your behalf. Regardless, you must be prepared to comply with any light gun instructions that you receive.

+1 for the backup radio. It's good to have something completely independent of the aircraft systems. The OP could also use a cell phone to call the nearest manned tower, regional control center, or 911.

Nope. With total blackout, if you can choose, do not go to an uncontrolled airport.

@Jpe61 Compared to a highway though?

Well compared to highway i'd take the uncontrolled, but thats a close one too :)

You guys must have some questionable uncontrolled airfields where you live. I immediately thought of a couple of fields near me that have nice lighting that's on all night, and zero traffic most evenings. Going to a field that's controlled all night is fine, but you're almost guaranteed to have more traffic (that can't see you). The tower should help provide separation, but you're putting faith in someone that you can't talk to, praying that they are doing their job, entering an area that you normally can't enter without making contact first, and waiting on instructions to allow you to land.

In North Texas, we are not so lucky. The pilot-controlled airports generally have their runway lights turned off or to their lowest intensity. You have to have a Comm radio to turn them on or to a higher intensity. Even the Class D airports will have minimal lighting after the tower closes. You would have to rely on moonlight and ramp/parking lights to illuminate the runway. Just the all night rotating beacon is not enough.

If I understand correctly the scenario you have given, your destination airport is the closest viable airport. But, the tower is no longer operational due to it being after hours. If this were the case, the airport will revert to a Class E or G, non-towered airspace. You can continue to land at that airport as if it were any other non-towered airfield. You are allowed to enter the airspace and land as long as you practice see-and-avoid visual separation from other aircraft. Enter the traffic pattern using one of the recommended methods from the AIM. Use the traffic pattern direction dictated in the sectional or chart supplement. You would not need to make any radio calls. If you are on an IFR flight plan, try to arrive at the airport as close to your Estimated Time of Arrival as possible.
For a loss of communication scenario, the FAR/AIM spells out pretty well the procedures to take. The issues you would face outside of that comes in three forms:

Is your electrical issue likely to cause any other emergency on your part (like a fire, a failure of another component, or a collision with another aircraft)?
Can you enter Classes A, B, C, or D airspace without clearance?
How are you going to turn the lights on at the destination runway?

Being on an IFR flight plan would solve many of these problems. On an IFR flight plan, ATC would also have provided you clearance through or to airspaces all the way to your destination. ATC would be looking for you. And, your radio silence would be noticed. ATC would know your ETA, and could arrange to have the runway lights turned on for you. Otherwise, you would need an alternate means to turn them on, like a handheld radio.
While a total electrical failure would render all but your magnetic compass, vacuum driven and pitot-static instruments useless, your engine should still function. Continue to aviate. The tools from my own flight bag list will help you to navigate, communicate, and mitigate risk:

An iPad or other tablet with a current EFB like Foreflight.
A backup tablet outfitted the same.
A portable PED battery bank with charging cords.
A red lens flashlight and/or headlamp.
A paper sectional of the area.
A US Chart Supplement.
Paper instrument procedure charts.
A handheld portable NavCom radio with ILS.
A fully charged cellphone.
A self-powered ADS-b in device such as a Stratus.
The phone numbers of airports and Approach in your area.

the intended destination airport

While other answers are excellent, one thing still deserves a mention:
Get-There-itis.
The urge to perform a flight, or complete a flight to plan, or simply divert to a preferred airport instead of a near one, has killed more than its share of pilots.
The idea is if you go to your planned airport, magic will happen and you’ll be able to land, and NOT have that fail and be forced to divert to ???, or worse, have a string of approach-fail-divert’s while you run out of gas.

key the mic seven times; squawk 7600

The radios run on electricity...
One fatal conceit that also kills pilots is the belief that nothing else will break. In this case, it’s a failure to understand the dependencies of the system.  But aircraft fires are the ultimate example: there’s no question that more systems will be affected, yet we’ve seen several crashes where pilots rejected going direct to the nearest possible divert airport, which would have worked.
An electrical outage is not as serious as a fire, but still, don’t ignore it, nor presume that the
stuff you are aware of is the only thing wrong with your aircraft, and nothing else will fail enroute.
Get it on the ground soon and safe.
That’s it. If there’s anything to learn from the above accidents, it’s that there’s no other variable in the equation.  Not overpriced FBOs, not airport facilities/immigration, not dealing with the military, and certainly not post-landing logistics to complete your travel.
So within reason, divert to an airport well able to take you.  Due to the likely impossibility of activating radio-controlled lights, such a field must be crossed off the list, unless there is simply no other choice and you think you can pull it off in moonlight.  Controlled commercial fields like Dulles are absolutely in-play, as are military fields.
Obviously if you have several good choices it is worth having a bit of a “pecking order” with military at the bottom, but don’t place too much importance on it.  If a base commander is grinding you about “why’d you pick us and not the well-equipped regional airport 3 miles away”, then “your landing lights were on, theirs weren’t” is a perfectly fine answer. As is, “I’m unfamiliar with the area, and did not know that airport existed”.
And, you are an emergency aircraft.  If you’re coming up on McCarran and you can see they have a very tall stack of planes on approach, you are an emergency aircraft. ATC will get them out of your way.


text:
What's a normal response delay for a paragliding vario?
I'm a paragliding pilot with P4 licence and I've purchased a 2nd-hand FLYMASTER B1NAV flight instrument for XC flights – mainly for logging the flights (route, distance, max. speed etc). It is an Altimeter-Variometer-GPS combo. As you know, these devices warn the pilot with beeps during climbing and sinking.
I'm using the device for a couple of months but I recently noticed an interesting thing: When I enter the thermal I first feel the climb with my harness and risers. But the device starts to beep with a delay of 1-2 seconds.
Is this normal?
I know it's an old and discontinued product. I've looked into its manual, but couldn't find any info about the delay. I don't want to rate this device as "broken", but I cannot be sure.

PS you'll probably get better answers by posting to a dedicated paragliding forum.

That is probably normal.  I notice a similar delay when flying with my Brauniger IQ Comp vario (lately mainly in sailplanes.)  Minimizing the delay is why the latest varios incorporate accelerometers as well as barometric pressure sensors.  Sounds like you've already checked the manual to see if there is some way you can decrease the interval of averaging, upon which the primary visual display and audio tone are based.  That adjustment is definitely possible with some variometers produced for hang gliding / paragliding use, but not with all.
Another way to get a quicker response time is to buy a vario that is even older.  For example, check out the "Litek Hummingbird".

That's normal for older varios. However it's not normal for current products.
An early form of vario is a flask vario:

As the instrument rises, the air in the flask will try and rush out of the openings since it will be at a higher pressure than the surroundings. As it rushes past the pith balls, one is forced upwards in the draft. The same thing happens in descent but the other ball is forced upwards.
There is obviously a lag due to friction and inertia.
Modern electronic varios use other sorts of sensor but they are still barometric sensors like this (i.e. they rely on air pressure to give us an indication of altitude and rate of climb).

In these flight instruments, electronic sensors measure the
rate-of-change of air pressure, from which climb rate can be
calculated.
Early varios used a simple needle display with a corresponding audio
signal. As things went digital designers were able to do more, adding
averagers and energy compensation. But everything still relied on a
pressure sensor. (source)

These typically have low lag. For example, the BlueFlyVario vario samples a a rate of 50Hz so the minimum lag is 20 ms. With older models perhaps 1 second of lag isn't unheard of.
Nowadays, the latest varios combine many sensors (predominantly an accelerometer and a barometer) but also GPS and gyroscopes to give near zero lag.
So while it's true that some older varios can have lag, it shouldn't be expected with modern instruments and it's definitely not what you should have to put up with.
This is a seven year old video showing zero-lag in a tiny vario.

Dunno whose doing all the dv'ing but keep in mind the question was about the normal behavior for an older instrument of a specific type, not about whether that represents the optimum possible design, or even the optimum attainable design at the time the instrument was produced.

The question was "What's a normal response delay for a paragliding vario?" A subquestion was related to that specific make and model. It would seem useful to the asker to have additional context.

Yes, that is perfectly normal. It's physically unavoidable to feel the lifting force, that sets a rise into motion, before that rise can be measured. The only faster way I could think of were to measure rope tension instead of altitude.
As for the duration of the delay: The manufacturer knows that there is some measurement noise (fluctuation), and needs to smooth it out. If they determined that the measurement might fluctuate within a 10 cm range in any given second, they will not alert you unless you have climbed 11 cm.

Why is it physically unavoidable? I don't think it is, after all that's precisely how an accelerometer works. Plus there are varios on the open market that do this.


text:
Has the construction team of the Northrop Grumann B-2 Spirit made use of the features of the German Horten Ho 229?
 1)
 2)
In the first picture, we can see the German-made Horten Ho 229. See also this video.
The second picture shows the American-made Northrop Grumman B-2 Spirit. See also this video
Clearly, both air wings show a remarkable similarity. The German plane looks much smoother though than the quite linear and edgy American one (is there a reason for this? Hasn't a smoothly formed plane less resistance?).
The Horten brothers, who supervised the construction and came up with the design, had no computers at their disposal like plane designers have these days. Every time some adjustments had to be made to make it fly better. In this BBC article one can read the plane was its time far ahead.
The designers and constructors of the NG B-2 Spirit did have computers and more advanced technology at their disposal to construct a working flying wing which clearly shows much resemblance with the wing developed decades before (maybe in a more "instinctive" way?).
My question is simple (I couldn't find this on the internet}:
Did the people who made the NG B-2 Spirit make use of the information of the Horten Brothers. Did they use the blueprints of the HH Ho 229?
Extra question: Why does the Northrop Grumann have such an "edgy", straight form, while the Horten has a smooth, curved form? Isn't curvature and smoothness better for the aerodynamics?

Reimar Horten applied to join the "paperclip" expat technologists in the US, and also in the UK, but was refused both. This despite working for the Brits for a time in Germany, in the immediate aftermath of war, and being interviewed by many in the industry. This must in part be down to an unsympathetic summary of his knowledge by a British official interviewer. On the other hand his chief rival and architect of the Me 163 Komet tailless fighter, Alexander Lippisch, had also been working on flying wings and was taken to the US.
One reason for this difference in perception of the two rivals was that Lippisch had fifteen years of solid financial backing and academic research programmes behind him, leading to a large pile of materials attesting to his standing. By comparison the Hortens had always struggled and much of their accumulated expertise was never given the resources to be written down and remained in Reimar's head or notes, at best published informally in gliding magazines. His rather high-handed "I don't need experts, I am the expert" attitude may have had some truth to it, but it lacked a visible evidential base and consequently was not believed.
As mentioned in another answer, Northrop's B2 was derived from the B-35/49 programme (The B-49 was just the B-35 with jets and mini-fins). That in turn derived from his work over the previous decade, when the Hortens were all but unknown to wider industry. He would have been far more aware of Lippisch, but even there they plowed fairly distinct aerodynamic furrows.
To return to Reimar Horten. In part due to the recent release of classified reports, the claim has arisen that he was able to design what is known as proverse yaw into his flying wings. Together with sweepback, this created a plane that was directionally stable. None of his WWII or earlier designs (that I can recall offhand) needed fins. Those of Lippisch and Northrop suffered from adverse yaw - a tendency to shy off course when banked into a turn - hence their constant need for fins. If this claim is true (and I have not seen the evidence), that would mark him out as the first designer since pioneer J W Dunne to fully conquer the stability of the finless aeroplane.
The B2 exchanges such aerodynamic subtleties for computer algorithms.

If the objective is very similar, good engineers will independently arrive at a very similar solution.
Yes, the Northrop engineers knew of the Go-229 / Ho-IX. But Jack Northrop has also played with flying wings before – witness the YB-35 and YB-49. Unfortunately, those designs "did not fly" with the conservative bureaucracy of the Air Force. While the Ho-IX was a very advanced concept, there was no "secret" in its design, so how a low RCS airplane should look like was quite obvious to the Northrop engineers.
That the B-2 looks more "edgy" is caused by more insights into stealth technology. While the Horten IX tried to minimize frontal area, used wings of wooden construction (which are transparent to radar energy) and Reimar Horten had planned to use radar absorbing charcoal, the B-2 uses edge alignment in order to reflect radar energy at specific angles, besides using radar absorbent material. When Northrop was designing the plane, it had a rhombic inner section with rectangular wings, much like what is now shown of the new B-21 design, but the small chord at the wing root created a structural weakness when the Air Force added a low level flying requirement. That only was overcome after Boeing got involved. Boeing engineers changed the planform to the current shape by adding more chord at the inner wing which resulted in the typical "W"-shaped trailing edge of the B-2.

B-2 design evolution and its Lokheed competitor (picture source)
After the B-2 production run had ended and after Grumman had merged with Northrop, a full-scale RCS model of the Horten jet was fabricated by Grumman engineers with modern techniques to simulate the aircraft as it would appear to electromagnetic energy. It was tested at a RCS test facility, using similar frequencies as those used in WW II. While the design did show a markedly lower RCS than comparable airplanes of the time, this can be fully attributed to its shape and the use of wood.

Horten IX replica on a sting at the RCS test range (picture source)
Reimar Horten was a bit dogmatic about his designs and insisted that they only use a wing and not even a vertical tail, even though this would had benefited its flight stability. As it turns out, a straight vertical tail produces in combination with a wing or the horizontal tail a nearly perfect corner reflector. While this dogmatism helped to reduce the airplane's RCS, it resulted in marginal lateral stability.

Very nice answer. Also the picture you showed. You write: so how a low RCS airplane should look like was quite obvious to the Northrop engineers.. But there are many other forms of flying wings, not so similar to the Ho IX.

@DescheleSchilder But very few of them have low radar cross section as an overriding design goal. The B-2 would not be a flying wing without vertical tail were it not for this one requirement.


text:
Can I get a first class medical with eyesight of -4.25/-1.00 diopters?
I'm wondering if I'm able to obtain the FAA 1st class medical certificate with the power of -4.25 and -1 in my eyes. I heard that the difference between the two eyes must not exceed 2 diopters.

From the FAA's website

The key line is "with or without correction". So as long as your vision is correctable to the standards given you are good to go. You can find the full AME guidelines here is you are curious.

For those wondering, -1.00 in diopter is roughly equivalent to 20/40.


text:
How do I follow an ILS glideslope on the ADI in Falcon BMS?
I'm currently flying the ILS landing mission in Falcon BMS, I'm practicing landing using the instruments (head down) and although I'm mostly OK with the LOC, I struggle to maintain a 2.5 degree glideslope.
In the training doc for Falcon BMS there is the following information:

ADI gives an angular reference to the position of the glideslope. Each
  dot on the left side of the ADI represents an angle of 2.5°

But I don't know how to achieve the above. I watched some YouTube videos but I didn't see anyone aiming for those dots on the ADI (yet they managed to land perfectly).
I don't want to chase the glide path bar on the ADI, so how do I hold a proper glideslope using the instruments?

Great answers below, but I don't think they emphasize using the VSI enough. Be aware of the instrument lag and don't fixate or chase it, but nailing this parameter is key.

The trick to flying a raw-data ILS is to find the pitch attitude that gives you the descent rate that achieves the target glide slope as far out as possible, then hold the attitude as you monitor the ADI, making small attitude changes and waiting for the result when corrections are required.
So try this procedure:

As the ADI comes alive in level flight, gradually lower the nose as the indicator approaches the middle index to an attitude that is giving about 6-700 fpm down The required descent rate depends on ground speed - a shallow glide slope like that going 130-140 kt will be somewhere around that descent rate; finding it by trial and error is easy enough (a normal 3 degree glideslope, which you are probably really referring to, will need about 750-800 fpm going that speed).  Note the pitch attitude in degrees and hold the attitude.
Monitor the ADI.  You want it to be very slowly creeping toward the target. If it stops above the target index or starts rising, you are descending a bit too fast.  Raise the nose 1 degree on the pitch index, hold the new attitude and wait. Vice versa if the opposite problem.  If it keeps moving the wrong way, change the pitch another degree and wait.
When the ADI is on the target, pitch a degree to stop it from moving, and wait.
At some point with these little tweaks you will find yourself on slope with the ADI not moving.  Note the pitch attitude and concentrate on holding that pitch attitude.
If the ADI starts to drift up or down, same deal, pitch up or down one degree and wait. If that's not enough, pitch another degree and wait.  And so on.  The key thing is to keep the corrections small and be patient.

As you get farther down the ILS the sensitivity goes up and the deviations become harder to track so it becomes critical to get sorted out as far out as possible and have the pitch attitude nailed as you get close in.  If you have the pitch angle and hold it the slope will generally take care of itself unless you encounter a change in wind that affects your ground speed.
The other thing is trim trim trim.  When you are on-target and on-speed, trim to hands off. Now only slight pressures are required to make corrections, and the "default" or relaxed, control input is the nominal correct one.

Thank you very much, I appreciate your time and answer <3

John K is correct.  Flying a glideslope indicator is a pitch attitude exercise.  I teach the exact same as John mentions in his steps.  PICK a pitch attitude and keep it.  If the glideslope does something unwanted, CHOOSE a different pitch attitude and keep it.  Keep doing this until the result is achieved.  The glideslope indicator is a tertiary instrument.... meaning it provides only trend information.  Use your primary and secondary instruments to fly the airplane.  In a steady state descent, the primary pitch instrument is vertical speed.  Secondary is the ADI.

Am I correct in assuming that you are using the Glideslope Indicator to measure your angle of descent. In other words, the wording of your question makes it sound like you believe the center of your Glideslope Indicator represents an angle of descent of 0°, and the next dot represents a descent angle of 2.5°.
The angle of descent of an ILS is set by the position of the transmitter equipment on the surface of the airfield. It is something that remains constant, and does not change unless someone on the ground adjusts the actual antennae on the surface of the airfield. The normal position of the ILS antennae are that the Localizer antennae are located at the departure end of the runway, facing the arriving aircraft. The Glideslope antennae are located along side the runway, normally abeam the precision approach aiming point (thousand footers), angled upwards approximately 3°. You can not change this from the aircraft.
Your goal is to keep the Glideslope Indicator centered during your entire descent from the Final Approach Fix. Some pilots will choose to intercept the Glideslope before descending from the Intermediate Fix altitude. In which case, you keep the Glideslope Indicator centered from there. If your indicator is positioned on the dot above center, you are flying below the 3° glideslope. If your indicator is positioned below the center, you are flying below the 3° glideslope.
Always intercept the Localizer before intercepting the glideslope. Beware trying to intercept the glideslope by descending into it from above. Nor should you try to intercept the glideslope before the Intermediate Fix or at an altitude above the Intermediate Fix altitude. You may encounter false signals, otherwise.
One trick to this is to have your aircraft fully configured prior to reaching the Final Approach Fix. This includes:

Gear lowered. Prop governor at the highest RPMs. And, flaps set for your descent.
Aircraft trimmed for your desired approach speed (preferably the ground speed indicated on your approach chart to time the Missed Approach Point in your aircraft speed category).
Power reduced and set to maintain a constant descent vertical speed for a 3° glideslope. This speed may be listed on your chart (depending on whether you use Jepp, NACO, etc.). A good rule of thumb is to multiply your ground speed in knots by 5. This will give you your vertical speed for a 3° descent in feet.
Switch on landing, position, and strobe lights. Adjust mixture for maximum power setting. Turn on the boost pump if required by your POH. Fuel selector on the proper tank. And, open carb heat and/or close cowl flaps if so equipped.
Stabilize pitch, roll, lateral direction (compensating for wind), power and airspeed (adjusting for half of gust factor).
Checklist
Start doing all of this 1-2 miles before the Final Approach Fix or when the Glideslope Indicator is a full to a half dot above center. This will give you time to complete everything in time to intercept the 3° glideslope stabilized.
Make your Final Approach Fix radio call to ATC or area traffic.
Maintain the lateral and vertical guidance ILS center  using small, smooth movements of the control yoke. If set properly the first time, you should not have to adjust the throttle until you are preparing to round out for landing or go-around.
Keep the ILS centered to within half a dot at all times. If you reach a full dot of vertical guidance, readjust your throttle. If you are at or beyond a full dot at MDA(H) or DA(H), either go-around immediately at the DA(H), or prepare for a go-around at your MAP.

Hi Dean, thank you all for the answers, by saying glideslope indicator you mean ADI?

@LittleWing - Actually, no. Count the Attitude Indicator as a separate (gyro or accelerometer driven) piece of equipment from the radio signal derived Localizer and Glideslope Indicators. You need a Localizer  receiver to make an LOC approach and an additional Glideslope receiver to make an ILS approach. You can make either an LOC or an ILS approach with an inoperative Attitude Indicator. Some Analog HSIs and almost all digital (glass cockpit) HSIs have all three incorporated into one instrument (or, at least the same space). You also need an operating Altitude Indicator for any flight.

@LittleWing - Partial Panel Approaches (equipment failure procedures) are the heart and soul of IFR training. You should be able to shoot an approach to minimums for a landing or go-around with only a Magnetic Compass, Clock, Altitude Indicator, and an ILS receiver and indicator. You would also need either an Airspeed Indicator or a Tachometer (one or the other). It is difficult, but possible. You will practice it a lot in IFR training. Either an Attitude Indicator or a Turn Coordinator is helpful during normal maneuvering and flight to the IAF and holding fix.

Ok, thanks. Is it correct to keep the same ground speed from FAF to the runway? In that case I could calculate my VS during a consist
ground speed.
Thanks

@LittleWing - You should keep approximately your same ground speed from FAF to MAP. Since you can not directly control your groundspeed, keep your power constant and your airspeed stable. Adjust it accordingly after your DA, MAP or VDP. You can determine your DA from your Altimeter and your MAP from your Clock. Monitor both in case one goes out. If you lose your glideslope, you can not descend below your MDA. If you lose your localizer but have your VOR, don’t descend below your circling minimum. If you lose all position references, immediately climb to your Minimum Sector Altitude.

Thank you so much for the detailed explanation - stay healthy <3


text:
Are there any aircraft powered by tip jets in the propeller blade?
I am familiar with tip jet powered helicopter experiments. Is there any aircraft that use/used this mode and would it be useful to use a tip jet driven prop on aircraft instead of piston or turbine power?

There was a study done on the use of tipjets in civilian aircraft in the 1950's, if I can find the source I'll edit it into this answer. In any case, the conclusions from that study were as follows:
Because of the fundamental inefficiency of subsonic ramjet propulsion, a tipjet-powered propeller "engine" in the 100 to 150 horsepower-equivalent range was completely uncompetitive with piston power. The fuel flow rate required to run the tipjet prop was excessive.
The tipjet-prop plane had extremely limited range if carrying the same amount of fuel as the piston plane, and no useful load if it carried enough fuel to match the range of the piston plane.

I would think having the mass of jet engines at the ends of propellor blades (which run at 5-8 times the RPM of a helicopter rotor)  would create horrendous gyroscopic effects, while having a jet (or pieces thereof) come off would create enough vibration to destroy the airframe.

true. also, if one jet flames out, the whole shebang goes out of balance. Tipjets are really only good for converting fuel into noise and hot air.

Did you manage to find study?

And could tip jets be powered by a conventional engine, through pneumatic linkage of some sort with compressor? There was some helicopter concept back in the 80's that worked in a similar way.

Hiller helicopters explored this extensively in the 1950's and '60s. Look up hot cycle tipjet and cold cycle tipjet.

@Opusci If a wing-mounted jet engine with bleed lines to the rotor tip counts, the Fairey Rotodyne would be a prime example.

Only experimentally, such as the CL400 tip ramjet experiments.  It doesn't really work because if one quits, your airplane turns into a pinwheel due to the long arm of the thrust  source from the yaw axis unless the wings are very short.  Not literally a pinwheel, but it'll want to roll over and crash pretty bad.  If they were out on the tips of wings with the kind of span you need to cruise efficiently at high altitude (as opposed to a stubby winged fighter), you'd need a rudder the size of Wisconsin to be able to control it single engine in a low speed departure climb.

I think the OP means jet engines on the tips of the propellors, not on the wingtips.

Ludwig Wittgenstein investigated the technology while at Manchester University, UK, and even took out a patent. But his experiments in the lab and on a local railway track came to nothing and he never built an aeroplane. He later became famous as a philosopher.
The idea has been revisited now and again ever since, but I never hears of a plane actually flying with a tipjet-driven propeller.


text:
Is it possible to define a "good landing" in terms of pitch angle and vertical speed?
Is there a specific combination of pitch angle and vertical speed at touchdown that would be usually be considered a "good landing" in a B737NG?

I changed your wording a little; don't hesitate to roll back or edit again if I changed it too much. And I removed your second question about what a long landing is because it would be best to ask that separately. We prefer to avoid having multiple questions in one on this site.

Probably, but there are many other factors as well, and "good" is pretty subjective.  For that reason I don't think the question can really be answered objectively.  Can you help us understand what you are trying to achieve?  (i.e. programming a simulator?)

This question and this one might be helpful.

No a good landing so much, but a "hard landing" yes, because of the need to assess whether or not to do special inspections, rap the crews' knuckles, and such.  When I was with a Regional OEM I used to help assess FDR downloads sent to us by a Chinese operator to tell them what happened (most operators did that sort of thing themselves).  The main factors are closure rate and touchdown G load as recorded by the FDR sensors, but speed and pitch attitude and other parameters were all part of the assessment.  New airplanes with ACMS record all that stuff and even flag bad landings.

John makes an excellent point:  That it is far easier to quantify a "bad" landing using definable criteria that would trigger overstress inspections, etc.  All others would be deemed acceptable, in keeping with the time worn adage that "a good landing is any one you can walk away from".

@MichaelHall And a "great landing" is one where you can use the airplane again.

Landing the CRJ200 was effortless, and the trailing link gear was very soft.  Occasionally  I could achieve a touchdown that was only apparent when the vibration of the wheels rolling could be felt, although this really wasn't an optimal thing to strive for, burning up 200 ft of rwy per second.  You had to work at it to get a landing that felt "hard".

@Terry IIRC a “good landing” is one where you can find all the bits.

A "good" landing with a 737NG as described in the Flight Crew Training Manual (FCTM) is flown with a pitch that has increased by 2 to 3 degrees during the flare. The resulting vertical speed is not specified, but will only depend on the airspeed at a given pitch increase. Remember, that a good landing requires a stabilized approach first, so you should cross the runway threshold at Vref + wind correction and at the correct height (usually 50 ft for typical glideslope).

Initiate the flare when the
main gear is approximately 20 feet above the runway by increasing pitch attitude
approximately 2° - 3°. This slows the rate of descent.
After the flare is initiated, smoothly retard the thrust levers to idle, and make small
pitch attitude adjustments to maintain the desired descent rate to the runway.
Ideally, main gear touchdown should occur simultaneously with thrust levers
reaching idle. [...]

Typically, the pitch attitude increases slightly during the actual landing, but avoid
over-rotating. Do not increase the pitch attitude after touchdown; this could lead
to a tail strike.
Shifting the visual sighting point down the runway assists in controlling the pitch
attitude during the flare. A smooth thrust reduction to idle also assists in
controlling the natural nose down pitch change associated with thrust reduction.
Hold sufficient back pressure on the control column to keep the pitch attitude
constant.
Avoid rapid control column movements during the flare. If the flare is too abrupt
and thrust is excessive near touchdown, the airplane tends to float in ground effect.
Do not allow the airplane to float; fly the airplane onto the runway. Do not extend
the flare by increasing pitch attitude in an attempt to achieve a perfectly smooth
touchdown. Do not attempt to hold the nose wheels off the runway.

(Boeing 737NG FCTM 6.10 - Landing, emphasis mine)
Typical touchdown vertical speeds are then between 60 and 180 ft/min as explained in this answer.


text:
How does one differentiate a "fly by" from a "fly over" waypoint?
I am referring more to Terminal Area Procedures (SID, STAR, Approach), rather than en route waypoints, airways etc. How do I know if such a waypoint is a "fly over" or not?
Especially for some RNAV procedures, where the turn to join the final approach course can be 90 degrees. I have already read the "Fly over or fly by question" but I did not find a reply to the above, although the example quoted and shown in that question was a very good example of what I am asking.

Are you asking what the chart symbols are? This question might also be relevant.

Are you referring to the waypoints as depicted on the FMC legs page? . . . or chart symbology? Remember FMC legs and vertical profile must be checked against the published procedure before shooting an approach.

I am referring to both actually, but specifically referring to SID, STAR and Approaches (both Instrument and RNAV) Does the FMC show the difference? And are they shown differently on the ND?

A flyover waypoint will have a circle drawn around it on a chart, whereas a fly-by waypoint will not. (Easy to remember: the circle looks like the O in Over)

The symbols for a fly-by and a flyover waypoint in aeronatutial maps and charts can be differenciated by the circle surrouning flyover waypoints.

https://skybrary.aero/articles/waypoint


text:
What is the difference between IAN and LNAV/VNAV?
Is there a real difference or benefit in using Integrated Approach Navigation (IAN) instead of LNAV/VNAV for a non-precision approach (NPA)?
Both give you lateral and vertical guidance during an NPA. Is IAN more precise?

A Non Precision Approach (NPA) flown with Integrated Approach Navigation (IAN) is not more precise than the same approach flown with LNAV/VNAV. The advantage of IAN is that the instrumentation and procedures are very similar to ILS (Cat I), which is the most common approach type flown for most airline pilots. Having a common set of indications on the PFD and procedures to follow improves flight safety.
The Boeing 737 Flight Crew Training Manual (FCTM) says:

IAN approach techniques are
similar to ILS approach techniques [...]
All IAN approaches provide the functions,
indications and alerting features similar to an ILS approach. Although non-ILS
approaches using LNAV and VNAV can still be performed, IAN is normally used
in place of LNAV and VNAV because of improved approach displays, alerts and
standardized procedures.

(Boeing 737 NG FCTM 5.60 - Approach and Missed Approach, emphasis mine)
The article about IAN on flaps2approach goes into a bit more detail:

Advantages of Using IAN
There are multiple advantages to an airline using IAN, the foremost
being flight safety. Unstable approaches contribute to many aircraft
accidents, and flight crews strive to always establish a stabilised
approach profile for all instrument and visual approaches.
The Global Position System has enabled stabilized approaches at many
airports and advanced features such as IAN take advantage of this
technology to provide consistent, intuitive displays that support
stabilized approaches.
18 Approaches Types to 1
Through the use of IAN, the number of approach types has been reduced
from 18 to 1, greatly simplifying the approach procedure and
minimizing the amount of time an airline needs to train pilots in
numerous approach types.  Time is money and utilizing advanced
technology such as IAN can increase airline productivity.
Additional Data - Increased Awareness
The distance to runway threshold, approach guidance information, and
vertical and lateral deviation markers are displayed when IAN is in
range of a designated runway.  Whether IAN is used or not, this
information provides additional guidance when executing an approach.
For example, when executing a VOR approach, this information has been
displayed on the Navigation Display (ND) as the distance to the actual
NAVAID (VOR) - which may or may not be aligned with the threshold of
the runway.  IAN will by default, display the lateral and vertical
deviation, and distance to the runway threshold, allowing for greater
precision during a non-automated approach.
These are but a few of the advantages to using the Integrated Approach
Navigation system.

(flaps2approach.com - Integrated Approach Navigation (IAN) - Review and Procedures)


text:
Is using a DERATE for Takeoff actually reducing the power of the engine?
When one chooses a DERATE for takeoff (TO-1 or TO-2 in the case of a B737), does the system actually reduce the available thrust of the engines, or is it computing a N1 that corresponds to the reduced (de-rated) thrust?
Referring to a B737NG for example, does a setting of "TO 89%" produce the same thrust as a TO-1 or TO-2 with the same N1 of 89%?

Do you want a general answer or a 737 specific answer?

A specific B737 answer would serve fine :-)

I cant' give you a 737 specific answer, but how DERATE or Flex Thrust is applied generally depends on whether the engine is FADEC or not.
If a non-FADEC, it's just an FMS computed bug target setting on the N1 indicators and you move the thrust levers as required to match N1 to the bug. So it's still the pilot actually setting thrust to a lower computer-provided target than normal (if the airplane has an autothrottle system, it's the autopilot doing that job on behalf of the pilot through thrust lever servos).
If FADEC, where you (or an autothrottle system) just move the thrust levers until they click into a detent of some sort for takeoff and let the FADEC computers directly control the engines to achieve a computed N1 setting, it's the computers controlling the engines in accordance with your thrust rating selection when you ask for TO thrust.  So in that case it's the pilot telling the computers what he/she wants, and the computers do the actual work.

Understood, this is how I thought it works. But my specific question was and is whether the same N1 setting produces different thrust depending on whether TO (26k), TO-1 (24k derate) or TO-2 (22k derate) has been selected. Forgetting about Assumed Temperature for this example.

No on a turbofan the N1 value is the primary indication of thrust and if thrust is reduced, the N1 value, the fan being the primary thrust source, will be lower.  Turbofans are just turboprops with fixed pitch many-bladed propellers (and even "propeller" reduction gearboxes on the newest ones), and like an O-200 with a fixed pitch prop, fan rpm is the primary power indicator.

The 737 is somewhere in between the non-FADEC and the FADEC cases you mentioned. It has EEC, but no detents for the thrust levers. The autothrottle servos set the exact thrust lever position for you on takeoff, but the pilots could overwrite it by pushing the levers further forwards.

@Bianfable i made some edits in response to your comment but you should perhaps provide that as an answer no?

@JohnK Thanks, that looks fine. I didn't answer because I wasn't really sure what OP wanted to know. I think your first comment actually answers what they wanted to know.

I am still not clear: My question is not about HOW to set TO thrust. Let me try and rephrase what I am looking for: Referring to the B737, does an FMC setting of TO (26k) and 89% N1 produces exactly the same Thrust with say a TO-1 (24k) or TO-2 (22k) and 89% N1? In other words, if the N1 is set to 89% in all cases, selecting TO (no derate), TO-1 (24k derate) or TO-2 (22k derate) makes no difference if it results in the same N1? Or Does the EEC actually derate the engines, so at the same 89% N1 it produces less thrust if TO-1 or TO-2 are selected?

Well that depends on what actual ran rpm 100% represents. If the derate modes reduce the fan speed that represents 100% N1 to be in line with 22/24K, then 89% is a thrust reduction as well, being 89% of the reduced 100% thrust level. So if normal 100% max thrust represents a fan rpm of, say, 4800, and 24K is 4400 rpm, then 89% also represents 89% of 4800 or 89% of 4400. In any case for non-FADEC the EEC just trims the fuel schedule electronically a little bit above the hydro-mech schedule, so I think it would still just be target indications that change. You need a 737 guy to answer this one.

What you write makes sense. I wish a 737 guy steps in and tells me how it works in the B737


text:
Why isn't the application of "carb heat" in initial piston multi-engine failure emergency procedures?
What is the rationale for not including the application of carb heat in the initial multi-engine airplane's engine failure procedure?
I've recently starting flying light multi-engine airplanes again and have been practicing the engine failure procedures.
I noticed in the POH of the aircraft I'm flying that it doesn't mention applying Carb Heat to the dead engine. So I looked at some other multi-engine POH emergency procedures and noticed that Carb Heat is mentioned sometimes, but in the trouble shooting checklist for restarting, after the initial procedure.
Shouldn't carb heat be applied as soon as possible, while manifold is still hot enough to heat the air to melt any potential carb ice?  Like immediately after pushing everything forward and getting gear and flaps up?
Alternatively, I can also see an argument that before you identify the dead engine, applying carb heat to both engines would decrease some precious power from the currently functioning engine. Are there other reasons for not using carb heat sooner?

Once your engine has stopped, carb heat isn't going to do you much good. I assume your "rough running" procedures identify to apply carb heat? Really once the point your engine performance has degraded to "not running", the manifold isn't creating heat (or exhaust flow) anymore and applying it probably won't do anything.

@RonBeyer I agree with you. That is actually why I think if you apply carb heat within a few seconds of detecting an engine failure, if it was due to carb ice, there might be enough heat in the manifold get it to sputter back to life and create more heat, etc. The prop is windmilling, it should still suck some hot air through the carb. Also, sometimes when you lose power in one engine, it might not be totally dead, but you're still going to have asymmetrical thrust and run through your checklist.

Partly because carb heat is ineffective once the engine is no longer making power, but mostly because the initial engine out procedure isn't intended as remedial action to get the engine running again; the drill is to make sure the airplane is configured to be able to climb (somewhat) in the moments after the failure, so the priority is everything balls to the wall, gear and flaps, identify, confirm, feather with the aim of establishing a climb foremost.
In any case, if you applied carb heat to both engines as part of the drill, the dead engine would be getting probably insufficient heat anyway, and the live engine will enjoy a few percent power reduction from the application of heat.  On a piston twin like a Seminole or Duchess at gross on a hot day, that alone may be the difference between barely climbing or descending, so that the remaining engine takes you directly to the scene of the crash as the old joke goes.

The first part of your answer is probably the most logical reason why its not in the initial checklist. The second part of your answer is the only thing I can think of as to why it wouldn't be prudent to use carb heat until after you "identify" the dead engine.

Perhaps.  On a twin engine jet it's the same thing.  The only actions taken initially on a failure after V1 is to continue the takeoff ensuring the good engine is at max thrust, raise the gear with positive rate, and fly a modified single engine departure profile with the shutdown procedure done when workload permits on the way up.  No remedial actions are tried until all that is done and you are at a safe altitude.

You may want to add the aircraft in question as it could be specific to the airframe/engine.
One consideration is that once an engine stops running there is no more airflow through the venturi as no air is being drawn in. In turn there will no longer be a temperature drop in the venturi so carb heat is no longer needed. It may also subsequently work against you during an attempted restart by creating an sudden over rich situation.

I'm flying a Grumman Cougar. The other aircraft I checked was the Piper Seminole POH which has the Carb heat on the engine restart troubleshooting checklist... which by that time I can't imagine it will do any good.


text:
Are there more refined rules-of-thumb for Top of Descent calculation, than the simple FL x 3?
Forgetting the excellent capabilities of VNAV for a moment and reverting to simpler days, is there a rule of thumb to further refine the FL x 3 rule for Top of Descent calculation, when there are excessive head or tailwinds?
Like so many miles to be added/subtracted to the distance for every x number of headwind or tailwind knots?
This is assuming you want to stay on your standard descent speed profile and not alter it.

Yes, there were refinements to it. In the 737-200, 3:1 was a 250 knot descent, while 280 knots was 2.5:1, and 320 knots was 2:1. The book also said add/subtract 1NM per 10 knots of tail/head wind, although that's a pretty rough wag.
The newer 737's are cleaner, so 3:1 is a better bet at the typical 280 kt descent, and slowing to 250 will flatten things out from there.
The old rule of thumb that 1NM = 10 knots slowed at idle & level flight still seems to hold well for the newer jets.

pre-VNAV/early VNAV days we used FL x 3 plus/minus 10% of avg wind component and added 15nm for decel if the vector/STAR/approach and landing was more or less 'straight in', or 10nm for a vector to base turn or 5nm for vectors equivalent to a downwind.
alternately,
FL divided by 3. +/- avg wind comp and add 5 nm for a straight in.
Keep recalculating and looking out for significant wind changes - worked pretty well.
For the latest generation jets I would add another 5 to 10 nm without hesitation, though the issue has become meaningless most of the time due STAR and traffic constraints. current day usage would be confined to figuring altitude loss over a distance to meet such constraints or because of such constraints.


text:
What does this NOTAM about a STAR mean?
When planning an IFR Flight into KTPA using the BRDGE 8 STAR, I saw this NOTAM:

!FDC 7/5458 (KTPA A1015/17) TPA STAR TAMPA INTL, TAMPA, FL BRDGE EIGHT
  ARRIVAL... BRDGE STAR UNUSEABLE BELOW 5000FT PIE VORTAC RADIAL 138
  UNUSABLE BELOW 5000' 1705151500-PERM

Would that mean that I can't use the LBV.BRDGE8 transition below 5,000, so then I would need to be higher on the en-route portion?
What does the NOTAM actually mean when I fly the STAR?

Check for additional NOTAMS concerning the PIE VORTAC.  It appears that, for whatever reason that VORTAC radial is no longer functioning well at lower altitudes and, for whatever reason, the FAA is opting to not repair it.  As it's a needed navigational aid for that STAR, the additional NOTAM applies.  I'd guess the Orlando FSDO is in the process of decommissioning that STAR and issued NOTAMS until then.
UPDATE: It appears that this VORTAC out in Clearwater, FL has been malfunctioning, causing aircraft to stray off course and overfly noise sensitive areas at low altitudes, causing the Tampa airport management to receive a great deal of complaints.  The FAA has up to now been faced with the repair tasks on that navaid.  But it appears that, with the gradual decommissioning of VOR stations throughout the country combined with the preeminence of GNSS navigation, they have elected not to make the repairs and just leave the VORTAC as is for the foreseeable future.


text:
What do Turnaround Supervisors do before departure?
Before the plane is able to take off, what calculations do Turnaround Supervisors have to do and what do they have to check before the plane departs?

It depends on the airline and their specific procedures. Turnaround supervisors are in charge of ensuring all ground services are performed correctly and safety. The turnaround supervisor is also responsible to verify the load placed onboard the aircraft matches what was specified on the loading instruction report. Calculations can vary between cargo and passenger flights, but usually cargo involves more calculation and observation to ensure the load is adequately secured. The turnaround supervisor may need to crosscheck the information on the loading instruction report and the loadsheet received in the cockpit to ensure the flight crew received accurate information necessary to calculate takeoff speeds.
The National Airlines crash in Afghanistan highlights a serious case where the training of the individuals responsible for securing and calculating the necessary amount of load restraint was grossly inadequate.


text:
Is this Corrected Mass Flow equation correct?
I have an engine air mass flow rate (322 kg/s) which I would like to convert to a corrected mass flow rate at 10000 feet.
I have tried using the equation found here. However, this article lacks any sources and I have struggled to find any other reliable sources online.
I have made an attempt using the equation in the article but have gotten a greater mass flow than 322, which doesn't make sense.
Is the equation in the article correct or am I just calculating this wrong?
For 10000 ft I get:
Temperature 268K
Pressure 69.6817 KPa
So
Theta = 0.9301 and Delta = 0.6877
Which gives a corrected mass flow of 451 kg/s.

The equations on Wikipedia are correct (see Flack, for example). I believe your error is in their interpretation. You say that you are given a mass flow rate and want to "convert [it] to a corrected mass flow rate at 10000 feet." But the direction you take the equations is as if you have a mass flow rate at 10000 feet and want to convert it to the mass flow at sea level. If the latter is what you intended, then I see no error. If the former, you need to invert the equation.


text:
Did some early jet engines catch on fire at higher power settings?
Recently I've being playing some IL-2 1946, and in this flight simulator jet engines had a strange problem where if I suddenly throttle up more than 60% the engines would catch on fire. Is this a real thing? The engines that this happens on are the Jumo 004 and the BMW 003 on the Me 262 and the He 162.


text:
What is the difference between en route and airway?
I am studying about airway now. But there are multiple terms that mean airway like enroute or air route. I don't know exactly what the difference is between them.
Airway, en route, air route, air path
I want to know the difference of meanings or definitions between above terms. Please tell me in detail.

Enroute: An aircraft that is on its way to its destination.
Air Route: A specific route that an aircraft takes, just like a car route, taking specific highways and roads to get to your destination. Planes do not go a straight line from their origin to destination.
Airway: A highway in the sky. That is what planes fly in their route. So for example 2 planes flying the V23 Airway would have them flying the same path on the airway specifically.

I've heard of ATS route (Air Traffic Service route) but never of "air route." Where did you see that?

In addition "en route" is a french expression meaning "on the/its way".


text:
What is the phraseology when leaving a TRSA?
When leaving TRSA what is the correct phraseology to tell ATC that radar service is no longer desired?

You can say "cancel radar service" (probably the most standard under ICAO), "cancel flight following," "request frequency change," or anything else that conveys the same general idea. If all else fails, plain English is always acceptable too.
Regardless of which you say, ATC's response should be "radar service terminated, squawk VFR, frequency change approved," same as in any other class E airspace.

On takeoff, tower will typically tell you to contact approach as you start your climb.  After you do that, and if VFR and not on flight following, you just report "Binghamton approach, Nxxxxx is clear to the east" as an example, and can add your altitude. Binghamton, NY TRSA is the nearest one I fly thru with any sort of regularity (couple times a year). Basically you can treat them like a Class C as the TRSA is likely to be centered around a towered airport, while Class D may or may not be.
If you ask for flight following prior to takeoff, Gnd control, or the tower, can set you up with a squawk code so that approach has you in the system already when you contact them.
I always use flight following when flying cross country, nice to have another set of eyes looking out for you, and it expedites handoff to Center, or the next approach control, depending on where you are.  We're also under a Class B shelf, so it can be busy.
There are still planes without ADS-B, some illegally, some not needing it due to staying out of radio required airspace, or due to not having electrical systems, so all due diligence helps.

OK, I hadn't heard the term TRSA for a couple decades, but looked on Skyvector and sure enough there it a TRSA around Binghampton, as well as a few other Northeastern cities.  I have not come across this term, or any depiction of US airspace other than A, B, C, D, E and G in a very long time.  Can somebody please point me to where this is defined?  (or maybe this is a better standalone question?)

@MichaelHall AIM 3−5−6. Terminal Radar Service Area (TRSA)
a. Background. TRSAs were originally estab- lished as part of the Terminal Radar Program at selected airports. TRSAs were never controlled airspace from a regulatory standpoint because the establishment of TRSAs was never subject to the rulemaking process; consequently, TRSAs are not contained in 14 CFR Part 71 nor are there any TRSA operating rules in 14 CFR Part 91.

@JScarry - I know the background having learned TRSAs and ARSAs and CZs long before the current airspace classification superceded them, I just had no idea any remnants still existed!  I'm curious why they didn't just convert to Class C.  Anyway, thanks for the AIM reference, I learned something new today.

Plenty of info on TRSA. I'm based at one. A simple question about phraseology. NBD There must be some kind of ratio on forums...tons of comments but few answers. Makes for fun reading, I guess.

Class C requires mode C and (as of last week) ADSB in or above plus two-way radio contact; TRSA all of those are optional, which makes AOPA lobbyists happy.

Just out of curiosity. Are there any Class D airspaces in the US that do not contain at least one towered airfield? When the tower is temporary or not continuously operated full-time, doesn’t the airspace revert to Class E or G when the tower is not operational? Or, so I thought. TRSAs remind me more of a Class D with optional (to the pilot) Class C privileges, services, and dimensions.

There is recommended verbiage per AIM 4-1-18-b.2:

If any aircraft does not want the service, the pilot should state “negative TRSA service” or make a similar comment, on initial contact with approach control or ground control, as appropriate.

In the United States, participation in radar services such as flight following by VFR traffic is not mandatory. It is recommended for pilots flying VFR as a non-regulatory service. Two-way communication for VFR traffic before entering and while within  Class B, C & D airspace, and within 4 miles of a towered airport below 2500 feet AGL, is still required. Outside of these areas, communication with ATC by non-participating VFR traffic is optional only. This also applies to airspace within the TRSA (communication with the underlying Class D is still required). Communication rules for IFR still apply to IFR traffic regardless.
If you are already participating in radar services like flight following as VFR, you can ”cancel” ”terminate” or ”discontinue” the service in plain English. There is no mandatory phraseology for the pilot. No reason has to be given.

According to ICAO DOC 444 12.4.1.10:

RADAR SERVICE TERMINATED DUE (instructions) (reason).

Welcome to AviationStackExchange. The document you cited seems to be directed at ATC as it’s target audience. It is for the use of ATC personnel when ATC is communicating with pilots. It is meant to be used by pilots solely as a reference to understand ATC communications, not as a guide for pilot phraseology. It contains the following statement, ”Note 1.—Although these procedures are mainly directed to air traffic services personnel, flight crews should be familiar with the procedures contained in the following chapters of the document:“ Stellar researching on your part, though. I commend you.


text:
What happens if the autopilot fails to initiate a flare?
What are the chances of autopilot failing to do a flare in an otherwise stable autopilot controlled approach and landing? Has it happened before and how was it dealt with?

Form aircraft technical log by captain: "Defect:  autoland fails to flare."  - Response by mechanic: "Action: this plane does not have autoland capability."

This deserves the answer: "You find out if the pilot is paying attention or not."

In Airbuses, the autopilot always performs an autoland after an ILS approach, unless the autopilot is disconnected by the pilots before landing. At 400 ft the autopilot modes freeze (indicated by "LAND" on FMA) and autoland can only be prevented by disconnecting autopilot or performing a missed approach. The "FLARE" mode activates by 30 ft. Should the "FLARE" mode not activate for any reason, pilots would perform a go-around.
My technical knowledge is not deep enough to tell how it would be possible that "FLARE" mode would not activate after "LAND", except if there would be some critical system failures, like dual autopilot fail or failure of the radio altimeter. In that case, it would also be indicated by a bright red AUTOLAND failure light.


text:
Am I required to be current in my aircraft type to start CFI training?
Do i have to be current on my type (Cessna 172) to start flying the flight instructor training course?

Cessna 172 is not a type

Welcome to aviation.SE! Are you asking about part 61 or part 141 training? If it's part 141, your school might have some currency requirements but you would need to ask them directly.

I am not meaning to be rude. I think there is a glaringly obvious issue with this question. If you want to get your CFI, you should be well versed in Title 14 CFR, especially parts 61 & 91. Or, you should at least be willing to research it. Your students will expect and deserve nothing less from you. If you are not planning to get your CFI. And, you are just asking out of curiosity, see my answer, below.

My thoughts also, word for word @DeanF.

The FAA does not require any type of currency to fly a non-turbine, single-pilot certified, light GA aircraft under 12500 pounds and fewer than 9 pax seat (excluding the pilot’s seat). There is a currency requirement to fly any aircraft IFR. And, there is a currency requirement to fly passengers. There is a currency requirement of 24 months for on your pilot certificate (license), though. This requires an official flight review with a CFI, DPE, etc.

You are not required to have any flight time or aircraft currency for CFI. You only need to have a current commercial or ATP certificate, and an endorsement for spin training. Your certificate Class and Category must match the aircraft in which you want to instruct. Type is not mentioned in the CFI part of the regs. You will need a type rating to be PIC in any aircraft requiring a type rating. A Cessna 172 does not require a type rating. See below.
The spin training may require additional hours beyond what is necessary for your commercial or ATP certificate. But, spin training can also be accomplished during your previous hours of training for any of your current certificates.

61.183 Eligibility requirements.
To be eligible for a flight instructor certificate or rating a person
  must:
(a) Be at least 18 years of age;
(b) Be able to read, speak, write, and understand the English
  language. If the applicant is unable to meet one of these requirements
  due to medical reasons, then the Administrator may place such
  operating limitations on that applicant’s flight instructor
  certificate as are necessary;
(c) Hold either a commercial pilot certificate or airline transport
  pilot certificate with:
(1) An aircraft category and class rating that is appropriate to the
  flight instructor rating sought; and
(2) An instrument rating or privileges on that person’s pilot
  certificate that are appropriate to the flight instructor rating
  sought, if applying for—
(d) Receive a logbook endorsement from an authorized instructor on the
  fundamentals of instructing listed in §61.185 of this part appropriate
  to the required knowledge test;
(e) Pass a knowledge test on the areas listed in §61.185(a)
(f) Pass a knowledge test on the aeronautical knowledge areas listed
  in §61.185(a)(2) and (a)(3) of this part that are appropriate to the
  flight instructor rating sought;
(g) Receive a logbook endorsement from an authorized instructor on the
  areas of operation listed in §61.187(b) of this part, appropriate to
  the flight instructor rating sought;
(h) Pass the required practical test that is appropriate to the flight
  instructor rating sought in an:
(1) Aircraft that is representative of the category and class of
  aircraft for the aircraft rating sought; or
(2) Flight simulator or approved flight training device that is
  representative of the category and class of aircraft for the rating
  sought, and used in accordance with a course at a training center
  certificated under part 142 of this chapter.
(i) Accomplish the following for a flight instructor certificate with
  an airplane or a glider rating:
(1) Receive a logbook endorsement from an authorized instructor
  indicating that the applicant is competent and possesses instructional
  proficiency in stall awareness, spin entry, spins, and spin recovery
  procedures after providing the applicant with flight training in those
  training areas in an airplane or glider, as appropriate, that is
  certificated for spins; and
(2) Demonstrate instructional proficiency in stall awareness, spin
  entry, spins, and spin recovery procedures. However, upon presentation
  of the endorsement specified in paragraph (i)(1) of this section an
  examiner may accept that endorsement as satisfactory evidence of
  instructional proficiency in stall awareness, spin entry, spins, and
  spin recovery procedures for the practical test, provided that the
  practical test is not a retest as a result of the applicant failing
  the previous test for deficiencies in the knowledge or skill of stall
  awareness, spin entry, spins, or spin recovery instructional
  procedures. If the retest is a result of deficiencies in the ability
  of an applicant to demonstrate knowledge or skill of stall awareness,
  spin entry, spins, or spin recovery instructional procedures, the
  examiner must test the person on stall awareness, spin entry, spins,
  and spin recovery instructional procedures in an airplane or glider,
  as appropriate, that is certificated for spins;
(j) Log at least 15 hours as pilot in command in the category and
  class of aircraft that is appropriate to the flight instructor rating
  sought; and
(k) Comply with the appropriate sections of this part that apply to
  the flight instructor rating sought.
61.31 Type rating requirements, additional training, and authorization requirements.
(a) Type ratings required. A person who acts as a pilot in command of
  any of the following aircraft must hold a type rating for that
  aircraft:
(1) Large aircraft (except lighter-than-air).
(2) Turbojet-powered airplanes.
(3) Other aircraft specified by the Administrator through aircraft
  type certificate procedures.

I think we can pare that answer down just a little bit to what is specifically related to a Cessna 172 and its use in obtaining a flight instructor certificate.

@Carlo Felicione - How’s that?

In other words the question was more narrowly focused on the use of a Cessna 172 for taking the practical test to become a flight instructor, as opposed to every single requirement for application to become a flight instructor

@CarloFelicione - The question asks nothing about the Checkride (practical exam). It does not even ask if you can fly the C172 during training. It asks if he has to be current on type to START the training COURSE. The question makes it sound like the OP thinks the CFI course has a flight component. Although you do need to know how to fly to commercial standards from the right seat, the CFI training is more about being able to teach and less about flying. There are many CFI courses that are ground only.

As far as the Checkride, there is no currency requirement when flying with a duly rated instructor or DPE. If the DPE is not acting as PIC, you will need an endorsement from an instructor to do so.

There is no type rating for a Cessna 172.  The only requirements by law (see 14 CFR §61.183) to use one to apply for a flight instructor certificate are that a person must hold at least:

A Commercial Pilot Certificate with an Airplane Single Engine Land category and class rating
An Instrument Airplane rating
Hold at least a valid Third Class Medical Certificate, or meet the requirements of §61.113 (i).

Day/night currency to carry passengers per 14 CFR §61.57 will not be required to undergo flight instructor training in the C172.

Could you please add info about the source for this, just to make the answer more credible as this is a case of rules and regulations.

You don‘t need a Third Class Medical any more—Basic Med will be fine.

For the training, yes.  But you will need an active medical if you intend to take the check ride.  It’s best to get that out of the way prior to spending big bucks on flight training.

@CarloFelicione In the US, you do not need a Third Class medical to take any  checkride—basic med will suffice. You can use basic med to instruct as well. I do agree that if you want to be a professional pilot, you should get a First  Class medical before you start your training if you want to fly for the airlines or Part 135. You’ll need a Second Class medical if you want to fly other commercial operations.

In my previous comment, I said that you only need basic med for any checkride, but what I meant to say is that you only need basic med for any checkride where you are taking the ride in an airplane that is covered by basic med. So you would need a Third Class medical for a mult-engine checkride or for a Type Rating ride, etc.

You can conduct PIC duties in a twin using BasicMed.   No regulation against it.  All you’re limited on is the aircraft must be less that 6000lbs, carry no more than 5 passengers, and remain below 18,000 ft and 250 knots.